Organic Chemistry : Carbonyl Reactions

Study concepts, example questions & explanations for Organic Chemistry

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Example Questions

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Example Question #651 : Organic Chemistry

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Determine the major product of the given intramolecular aldol reaction.

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Possible Answers:

II

IV

I

None of these

III

Correct answer:

II

Explanation:

Keep in mind the following principles: Cyclization is favored when a five/six-member ring may be formed. Addition at an aldehyde is favored relative to the same reaction at a ketone. 

As a result, abstraction of a hydrogen bound to carbon 6 (an alpha-carbon) is favored since the resulting carbanion may attack the aldehyde (carbon 1) to form a six-member ring, resulting in compound II. Compound I results from abstracting a hydrogen from carbon 2, generating a carbanion which may then attack the ketone. Based on the latter of the above principles, this is a minor product.

Example Question #2 : Carbonyl Reactions

What is the final organic product of the reaction shown?

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Possible Answers:

II

III

V

IV

I

Correct answer:

I

Explanation:

First step: Friedel-Crafts acylation of benzene

Second step: Formation of enolate

Third step: aldol addition (enolate attacks carbonyl carbon in benzaldehyde)

Fourth step: neutralization of anion and dehydration forming alkene

Example Question #11 : Specific Reactions And Named Reactions

Esterification

What is the product of this reaction?

Possible Answers:

3

Ester

2

6

2butanone

Correct answer:

Ester

Explanation:

This is a classic esterification reaction. Esterfication occurs when a carboxylic acid and an alcohol are reacted together. Only one answer choice is an ester. 

Example Question #1 : Carbonyl Reactions

What is the final organic product of the reaction shown?

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Possible Answers:

III

II

V

I

IV

Correct answer:

III

Explanation:

First step: esterification

Second step: reduction

Third step: neutralization

Fourth step: oxidation to aldehyde

Fifth step: alkene metathesis

Example Question #1 : Help With Wittig Reactions

All of the following are characteristics of a Wittig reaction except __________.

Possible Answers:

it results in the exclusive formation of trans double bonds

it involves the reaction of a phosphonium ylide with a carbonyl

it proceeds through a phosphaoxetane intermediate

it produces a trialkylphosphine oxide or triarylphosphine oxide as a by-product

it results in the formation of a carbon-carbon double bond

Correct answer:

it results in the exclusive formation of trans double bonds

Explanation:

The Wittig reaction involves the reaction of a phosphonium ylide (generated by treating a phosphonium salt with a strong base) with a ketone or aldehyde.

The reaction proceeds through a phosphaoxetane (4-membered ring containing both phosphorus and oxygen) intermediate to generate a new compound containing a carbon-carbon double bond, plus a phosphine oxide byproduct. It does not form trans double bonds exclusively; sometimes, a mixture of cis and trans isomers are obtained, and sometimes the cis isomer is the predominant product. 

Example Question #1 : Help With Haloform Reactions

Which of the following best summarizes the haloform reaction?

Possible Answers:

The enolate of a dicarbonyl compound attacks a beta carbon of an alkene

A carboxylic acid reacts first with then with water

The enolate of an ester attacks another ester

A methyl ketone is treated with iodine and

An alkyl halide reacts first with the phthalimide ion, then with

Correct answer:

A methyl ketone is treated with iodine and

Explanation:

The haloform reaction requires a carbonyl with a terminal alpha carbon. A hydrogen gets abstracted, and the enolate is formed. A halogen attacks the alpha carbon, and the ketone is reformed. This occurs three more times until the carbon has bonds to three halogens. Then the carbon leaves, forming a carbanion, and the base attacks the carbonyl carbon. An ester is formed.

Example Question #1 : Carbonyl Reactions

Which of the following results in a single ketone product following acid catalyzed hydration?

Possible Answers:

5-decyne

3-decyne

4-decyne

2-decyne

None of these answers

Correct answer:

5-decyne

Explanation:

During acid catalyzed hydration, a hydroxy group replaces one of the bonds in the triple bond and a double bond is formed. This is called an enol. The enol naturally turns into a ketone in a process called tautomerization. The hydroxy group can attach to either carbon across the double bond, and naming is done so that substituents have the lowest numbers. Only on 5-decyne will result in a single product, as no matter which carbon the hydroxy group bonds to, it is still on carbon 5. Thus, the only final product is 5-decone.

The other answer options will still react, but will form multiple products due to lack of symmetry.

Example Question #21 : Specific Reactions And Named Reactions

What is the product of the reaction shown?

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Possible Answers:

III

V

I

II

IV

Correct answer:

IV

Explanation:

First step: bromination across the double bond

Second step: double dehydrohalogenation and removal of terminal alkyne hydrogen

Third step: neutralization of the molecule

Fourth/fifth step: hydroboration/oxidation, followed by keto/enol tautomerization

Example Question #1 : Help With Saponification

What is a product when propyl-butanoate undergoes saponification?

Possible Answers:

Butanol

Butyl propanoate

Propanol

Propanoic acid

None of these

Correct answer:

Propanol

Explanation:

When naming esters, the root word in the name describes the carbon chain that carries the carbonyl. Saponification describes the breaking up of an ester. This yields an alcohol and a carboxylic acid. The chain with the carbonyl is butyl, so the carboxylic acid will be butanoic acid. That means the side with the alcohol will be propanol. 

Example Question #1 : Help With Hydrolysis And Condensation Reactions

Which of the following best summarizes a Claisan condensation?

Possible Answers:

The enolate of an ester attacks another ester

An alkyl halide reacts first with the phthalimide ion, then with 

A carboxylic acid reacts first with then with water

A methyl ketone is treated with iodine and 

The enolate of a dicarbonyl compound attacks a beta carbon of an alkene

Correct answer:

The enolate of an ester attacks another ester

Explanation:

The most acidic hydrogen of the ester gets abstracted and the enolate form of the compound is attained. The electrons from the carbon-carbon double bond attack the carbonyl carbon of the other ester. Deesterfication occurs in this same step. The final product has one ketone and one ester.

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